Adding tests.py
Fixed some imports.

Fixed some imports.

Fixed some imports.

Fixed some imports.

Fixed some imports.
Added array of data years to WeaArray.
Added .gitignore.
Added some tests for 'years' array.
Added some tests to cover units conversion of WeaArray.
Coverage ignore.
Use xrange.
Added test for reading header of WeaFile.
Added test for returning latest data in a WeaFile.
Added the year to the result of WeaFile.latest_data().
Added WeaFile.get_datetimes() to return an array
of all datetimes in a data file.